This invention relates to a method for quantifying and measuring the optical anisotropy of a dielectric material such as a fibrous glass-reinforced plastic (FRP) material by use of a microwave.
In a composite material such as FRP which is composed preponderantly of a dielectric substance, it is the orientation and quantity of reinforcing fibers present in the resin that have the greatest effect on the mechanical characteristics of the material. When FRP articles are produced by the molding methods using sheet molding and bulk molding compounds or by the spray-up method, the reinforcing fibers contained therein tend to lack uniformity in orientation.
Heretofore, FRP articles have been tested for orientation and content of reinforcing fibers by destructive inspection based on combustion, decomposition, etc. Thus, establishment of a method for non-destructive inspection has been desired.
It is an object of this invention to provide a method for measuring the optical anisotropy of an opaque dielectric material such as an FRP article without necessitating destruction of the article.